Add Signing Commits in Git server

[rcarrata]

Include signing of the commits in Git Servers using PGP:

• in Gitea -> https://docs.gitea.io/en-us/signing/
• in GitHub -> https://docs.github.com/en/authentication/managing-commit-signature-verification/signing-commits

[rcarrata]

Working Example to Integrate -> https://rcarrata.com/openshift/secure-argo-supply-chain/